Dispersion and strength parameter of nano-sized bubbles in copper investigated by means of small-angle X-ray scattering and transmission electron microscopy

Nano-sized bubble dispersion in copper was achieved by a powder metallurgy method based on ball milling and spark plasma sintering. The microstructure of bubbles was evaluated by using Transmission Electron Microscopy (TEM), and the bubble size and interspacing were further quantitatively determined from small-angle X-ray scattering (SAXS) measurement. From TEM observation, the average radius of bubbles is 2 nm and their interspacing is 75 nm, while according to SAXS measurement, the radius is found to be 1.5 nm and the interspacing is 54 nm. By combining those parameters with the bubble distribution and Vickers hardness, the obstacle strength factor was evaluated as 0.23 by using TEM result, and 0.16 by using SAXS data. This suggested that bubbles could impede dislocation motion.